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High Resolution Paleolake-Level and Paleoclimate Reconstruction from Integrated Geologic, Glacial, Tectonic, and Hydrologic Modeling of the south-eastern Sierra Nevada
AuthorBacon, Steven Neal
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A new approach to developing a continuous paleolake-level curve for Owens Lake in the south-eastern Sierra Nevada during last 50,000 years integrates lake-core data and shoreline geomorphology with wind-wave and sediment entrainment modeling of lake-core sedimentology that is corrected for tectonic ground deformation. An 11,500-year time-series of reconstructed changes in precipitation and snowpack was then produced from a watershed-lake water balance model of the paleo-Owens River-Lake system. Paleoclimate simulations were performed at 100-yr time steps using adjusted 800-meter historical climate data. The water balance model developed in this dissertation improves on existing paleohydrologic models for the region through use of a continuous lake-level calibration curve and incorporation of (1) a paleotemperature dataset corresponding with local glacial deposits; (2) changes in paleo-solar insolation; (3) glacial ice/perennial snow accumulation; (4) salinity of paleolake water; and (5) surface runoff gains and losses. The simulation of hydroclimate during the Holocene is summarized by precipitation ranging from ~74 to 159% of historical baseline (WY1896–2015) with temperature anomalies ranging from -1.5 to 0.31°C. One of the principle findings of this research is the south-eastern Sierra Nevada was cooler and persistent droughts were not as severe during the late Holocene compared to previous estimates made from paleohydrologic modeling of other lakes in the region that are controlled by tree-ring proxy records. The application of elevated temperatures and lack of accounting for losses from snow sublimation and snow storage, plus losses from channel percolation in other models produces overestimates in the severity of droughts. The new Holocene hydroclimate record can be used to support other paleoclimate archives in the western U.S. by providing high-resolution quantitative estimates of regional hydroclimate variability.